State Department official David Shear told a congressional panel that the United States will "continue to stand by our commitment" under US law to provide Taiwan with weapons to defend itself.

"Taiwan must be confident that it has the physical capacity to resist intimidation and coercion in order to engage fully with the mainland," said Shear, the deputy assistant secretary of state for East Asia.

Testifying before the US-China Economic and Security Review Commission, US officials declined to say if the Obama administration would approve a top item on Taiwan's wish-list -- F-16 fighter-jets.

Despite his drive to repair relations with Beijing, President Ma Ying-jeou has pitched for F-16s to refurbish Taiwan's aging fleet. A recent report by Taiwan's defense ministry found that China has gained an edge in air power.

Michael Schiffer, the deputy assistant secretary of defense for East Asia, said he "didn't want to suggest a decision one way or the other" on the F-16s.

China has been ramping up military spending for years as part of a modernization drive for its People's Liberation Army (PLA).

Despite China's growing interests around the world, "we believe that the primary focus of the PLA build-up remains oriented on preparing for contingencies in the Taiwan Strait," Schiffer said.

"It appears Beijing's long-term strategy is to use political, diplomatic, economic and cultural levers to pursue unification with Taiwan, while building a credible military threat to attack the island if events are moving in what Beijing sees as the wrong direction," he said.

China also appears content not to attack Taiwan if it believes it will achieve its goals in the long run but is determined to pose a "credible threat" to pressure the island, Schiffer said.

Taiwan is ruled by nationalists who fled China in 1949 after losing the mainland's civil war. Beijing considers the island part of its territory awaiting reunification, by force if necessary.

David Shlapak, an analyst at the Rand Corp. think tank, said that the chances China could deliver a "knock-out blow" to Taiwan's air force at the start of a conflict have "increased substantially in recent years."

"China is assembling a military capable of providing the leadership in Beijing with credible options for the use of force against Taiwan, even in the face of US opposition," Shlapak told the panel.

China strongly opposes US arms sales to Taiwan, arguing that they run counter to the US recognition in 1979 of Beijing as China's sole government.

China responded sharply to the arms sales in January, warning that the United States was setting back relations and -- in a new step -- explicitly threatening sanctions on US companies involves in the contracts.

But Shear said that China's reaction "did not exceed our expectations."

"As far as I know, the Chinese have not implemented that threat. They have not yet imposed any sanctions on US firms," Shear testified.

Some US-based China watchers believe that Beijing may have concluded that it went too far in antagonizing Obama, who in his first year put off decisions certain to irk the growing Asian power.

China criticized Obama in February when he met with Tibet's exiled spiritual leader the Dalai Lama but made no concrete threat of retaliation.

that means with PLA increasing it's firepower especially when considering the growing profile of it's ballistic missie force it is possible ,also taking into account the geographical proximity ,that china can "some day" take over taiwan or is it that through constant arm sales of defensive weaponry taiwan is capable to resist it?